Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 235-252).

Advances in recording technologies now allow us to record populations of neurons simultaneously, data necessary to understand the network dynamics of the brain. Extracellular probes are fabricated with ever greater numbers of recording sites to capture the activity of increasing numbers of neurons. However, the utility of this extracellular data is limited by an initial analysis step, spike sorting, that extracts the activity patterns of individual neurons from the extracellular traces. Commonly used spike sorting methods require manual processing that limits their scalability, and errors can bias downstream analyses. Leveraging the replication of the activity from a single neuron on nearby recording sites, we designed a spike sorting method consisting of three primary steps: (1) a blind source separation algorithm to estimate the underlying source components, (2) a spike detection algorithm to find the set of spikes from each component best separated from background activity and (3) a classifier to evaluate if a set of spikes came from one individual neuron. To assess the accuracy of our method, we simulated multi-electrode array data that encompass many of the realistic variations and the sources of noise in in vivo neural data. Our method was able to extract individual simulated neurons in an automated fashion without any errors in spike assignment. Further, the number of neurons extracted increased as we increased recording site count and density. To evaluate our method in vivo, we performed both extracellular recording with our close-packed probes and a co-localized patch clamp recording, directly measuring one neuron’s ground truth set of spikes. Using this in vivo data we found that when our spike sorting method extracted the patched neuron, the spike assignment error rates were at the low end of reported error rates, and that our errors were frequently the result of failed spike detection during bursts where spike amplitude decreased into the noise. We used our in vivo data to characterize the extracellular recordings of burst activity and more generally what an extracellular electrode records. With this knowledge, we updated our spike detector to capture more burst spikes and improved our classifier based on our characterizations.

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Neural communication is imperative for physical and mental health. Dysfunction in either ionic signaling or chemical neurotransmission can cause debilitating disorders. Thus, study of neurotransmission is critical not only to answer important fundamental questions regarding learning, decision making, and behavior but also to gain information that can provide insight into the neurochemistry of neurological disorders and lead to improved treatments. The work presented herein describes the development of techniques and instrumentation to enable advancements in neuroscientific inquiry. The effect of different temporal patterns and durations of simulation of the prefrontal cortex on dopamine release in the nucleus accumbens was examined and revealed a complex interaction that can help improve deep brain stimulation therapies. A measurement platform that combines electrophysiological and electrochemical techniques is described. The instrumentation is capable of concurrent monitoring of neural activity and dopamine release in vivo and in freely moving rodents. Analysis techniques to allow absolute quantification of tonic dopamine concentrations in vivo are detailed and the temporal resolution of the technique was vastly improved from ten minutes to forty seconds. An instrument that can simultaneously probe both dopamine and serotonin dynamics in either of their two temporal modes of signaling (tonic and phasic) using either fast-scan cyclic voltammetry or fast-scan controlled-adsorption voltammetry at two individually addressable microelectrodes is described. Together these new tools represent a significant step forward in the field of neuroanalytical chemistry by enable multiple brain regions, signaling modes (ionic flux in addition to both tonic and phasic neurotransmission), neurochemicals, and to be measured together.

Despite substantial progress in the area of depression research, the current treatments for Major Depressive Disorder (MDD) remain suboptimal. Therefore, various medications are often used as augmenting agents in pharmacotherapy of treatment-resistant MDD. Despite the relative clinical success, little is known about the precise mechanisms of their antidepressant action. The present work was focused on describing the effects of three drugs with distinctive pharmacological properties (pramipexole, aripiprazole, and quetiapine) on function of the monoaminergic systems involved in the pathophysiology and treatment of MDD. Reciprocal interactions between the monoamines serotonin, norepinephrine, and dopamine systems allow the drugs targeting one neuronal entity to modify the function of the other two chemospecific entities. Electrophysiological experiments were carried out in anaesthetized rats after 2 and 14 days of drug administration to determine their immediate and the clinically-relevant long-term effects upon monoaminergic systems. Pramipexole is a selective D2-like agonist with no affinity for any other types of receptors. It is currently approved for use in Parkinson’s disorder and the restless leg syndrome. Long-term pramipexole administration resulted in a net increase in function of both dopamine and serotonin systems. Aripiprazole is a unique antipsychotic medication. Unlike all other representatives of this pharmacological class that antagonize D2 receptor, this drug acts as a partial agonist at this site. Chronic administration of aripiprazole elevated the discharge rate of the serotonin neurons, presumably increasing the overall serotonergic neurotransmission. Like aripiprazole, quetiapine is one of three atypical antypsicotic drugs approved for use in MDD. Prolonged administration of quetiapine led to a significant increase in both noradrenergic and serotonergic neurotransmission. Importantly, the clinically counter-productive decrease in the spontaneous firing of catecholaminergic neurons, induced by SSRIs, was overturned by the concomitant administration of both aripiprazole and quetiapine. The increase in serotonergic neurotransmission was a consistent finding between all three drugs studied herein. In every case this enhancement was attained in a distinctive manner. Understanding of the precise mechanisms leading to the amplification/normalization of function of monoamines enables potential construction of optimal treatment strategies thereby allowing clinicians greater pharmacological flexibility in the management of depressive symptoms.

Skeletal muscle has been used for biomechanical assist in experimental and clinical studies. Central to the success of these procedures is the generation of sufficient muscle force for the lifetime of the subject. Burst (tetanic) stimulation results in summation of individual twitches and generates higher power output. However, the superiority of paraneural versus intramuscular as well as proximal versus middle and distal intramuscular stimulations remains unclear. Electrophysiological mapping and mechanical performance of seven canine latissimus dorsi muscles were analyzed. The mechanism of higher tension generation produced by: (1) increased temporal summation; (2) greater motor units activated; or (3) result of both were determined. The parameters primarily dependent on the number of activated motor units are significantly greater following paraneural and proximal intramuscular stimulations. The parameters mainly related to temporal summation are not different between various electrode configurations. For intramuscular stimulation, it is the location of interelectrode field rather than the location of the cathode perse that determines the mechanical performance of the skeletal muscle. Furthermore, tension development of skeletal muscle is primary nerve activation rather than direct muscle stimulation. The higher tension generation that resulted from different electrode configurations is produced by activating a higher number of muscle fibers through the neuromuscular junctions.

京都大学 / 0048 / 新制・課程博士 / 博士(生命科学) / 甲第19143号 / 生博第326号 / 新制||生||43(附属図書館) / 32094 / 京都大学大学院生命科学研究科高次生命科学専攻 / (主査)教授 渡邉 大, 教授 影山 龍一郎, 教授 渡邊 直樹 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

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There are forty registered organophosphates in the United States and they range from pesticides and insecticides to nerve agents or neurotoxins such as sarin. Organophosphates (OP’s) have been used in chemical warfare for years and tend to lead to death due to an attack on the nervous system. Chemical assays and mass microscopy have been used to assess the concentration of OP’s in the environment, but both methods require the body to metabolize the OP first, which can be detrimental to the victim. It is crucial to come up with a method to investigate and detect these neurotoxins without causing harm first. There have been several studies presented in the literature that use medicinal leeches and sharp electrode electrophysiology to study the function of the motor end plate. Kuffler, Potter and Stuart have all conducted studies using the medicinal leeches to do so. They mapped out the cells within the leech ganglion as well as created an atlas of the entire leech anatomy, and demonstrated the electrical connection between the motor neuron and longitudinal muscle fibers. Using the knowledge they have provided, a medicinal leech and sharp electrode electrophysiology can be used to investigate the effects of organophosphates on the nervous system. Before this can be achieved a dissection preparation must be implemented that can be utilized in electrophysiological experiments and that demonstrates the electrical connection between the motor neuron and muscle fibers. This thesis outlines the implementation of the medicinal leech dissection preparation described above. The preparation removes one ganglion from the leech, leaving the roots attached to the portion of the muscle wall it innervates. To demonstrate the preparations validity, sharp electrode electrophysiology is performed using a current clamp and discontinuous single electrode voltage clamp (dSEVC). A current pulse stimulates the motor neuron and a voltage recording is obtained from the ganglion as well a current recording from the muscle wall. The electrical connection is therefore demonstrated. This dissection preparation and electrophysiology experiment are written up in a procedural manner so that another individual could repeat the experiment. The next logical step would be to use these procedures to perform OP nerve agent experiments to investigate the effect of OP’s on the neuromuscular junction.